1. Field of the Invention
The invention relates generally to numerical display apparatus and more particularly to apparatus for automatically converting a shaft rotation into digital signals for computer processing and for display on an operator's reference indicator.
2. Description of the Prior Art
In the prior art, conversion of shaft angle into a digital representation has been accomplished by using a shaft-driven synchro and associated electronic analog-to-digital conversion apparatus, by a coded wafer contacting switch, or by a binary coded optical shaft encoder. The first approach demands the use of a synchro data transmitter that must be precise and electrically balanced and which is therefore expensive. In addition, analog-to-digital converters are known to be sensitive to temperature and to other ambient effects unless suitable compensation is made. While they are fundamentally simple, coded wafer contacting switches exhibit electrical arcing and contact bounce at least after a period of use and thereby cause undesirable errors in associated electronic equipment. Commercially available optical shaft encoders are too large for incorporation in locations such as aircraft control panels and are, in addition, quite expensive.